A concussion, which is a form of mild traumatic brain injury, occurs after a blow to the head. The brain is surrounded by fluid and protective membranes called meninges, which usually cushion the brain. During an impact, the brain is pushed against the inside of the skull and can be bruised.
        
             
        
        
        
Here light ray strikes to interface at an angle of 45 degree and then refracts into other medium such that it will bend towards boundary.
So here the angle of incidence will be less than the angle of refraction as light moves towards the boundary after refraction which mean it will bend away from the normal
here it can be said that medium 2 will be rarer then medium 1
So here the possible options are
1. Water  
Air
2. Diamond  
Air
So in above two options medium 1 is denser and medium 2 is rarer
 
        
             
        
        
        
Gravity is a non contact force , jump from a little high place (don't do that :P) , you wont just get stuck in the air you will fall down , this is gravity you dont need any contact 
        
             
        
        
        
Answer:
v = 87.57 m/s
Explanation:
Given,
The initial velocity of the car, u = 0
The final velocity of the car, v = 60 mi/hr
The time period of car, t = 8 s
                                          = 0.00222 hr
The acceleration of the car is given by the formula,
                                        a = (v -u) / t
                                            = 60 / 0.00222
                                             = 27027 mi/hr²
If the car has initial velocity, u = 50 mi/hr
The time period of the car, t = 5.0 s
                                          = 0.00139 hr
Using first equations of motion
                                       <em> v = u + at</em>
                                           = 50 + (0.00139 x 27027)
                                           = 87.57 mi/hr
Hence, the final velocity of the car, v = 87.57 mi/hr
 
        
             
        
        
        
Answer:


Explanation:
In order to calculate the equivalent spring constant we need to use the next formula:

Replacing the data provided:


Finally, to calculate the frequency of oscillation we use this:

Replacing m and k:
